The explanation is very thorough and helpful. However, the answer assumes that earth and everything on earth is one system. Earth is an object and all the superstructures on it, all the life plying on it is attached to it or kept on it. When Earth is spinning everything is spinning with it with the same velocity. Now, when Earth stops due to Newton's first law of motion everything will keep on moving with the intertia they have (470 m/sec). everything will get thrown off, it is similar to a train stopping and you getting thrown off. 470m/sec is huge, it would be like a unidirectional earthquake. Everything will be devastated but structures that are low in high and deep might survive. Basements will be all fine. Skyscrapers will be dusted to ground. Also, supersonic winds will be blowing and things will be moving with the wind as both will have similar velocity.

Kindly review this and let me know if this makes sense. I think the answer in the book is correct but we can refine the reason.

I was going to ask which this was, why you weren't using the thread that it undoubtedly already has.. Half remembering something about it, but not able to find it online by a quick browse, assuming you've not distorted the title too much to confuse me... But it's from the book, I think you're saying, explainibg why I found it familiar (have read it) but inaccessible (ṭhen gave it as a birthday present!)... Not sure we have a standard filing procedure for What-Ifs not in the web set.

Still, first post. Welcome. And must have gotten past the mods' newbie-authorisation process. I hope your boldness is going to be rewarded at least as well by the rest of the ragamuffins who reside here. Give me a day or two, and I'll borrow back my book (or find another copy) and may have something more constructive to say!

The book presents it as the most reasonable definition of earth vs. air; that is the earth and every solid or liquid object on its surface. Going beyond that you then need to define what is "part of the earth" and what is not? Do you count animals and people as part of the earth? What about buildings? What about trees? What about bodies of water? What about hills and mountains? What about rocks and other things that are just resting on the surface? If you choose another distinction then things go from bad to worse (or possibly better) pretty quickly.

The first step in that direction would be that the earth and everything attached to it (i.e. includes buildings, rocks, dust, plants, bodies of water etc. excludes animals, people, vehicles, etc.), in which case all humanity gets flung with the air; most of us getting thrown against nearby buildings, helping the wind to uproot them (people in tunnels also die because of this). People who miss the buildings will end up getting smeared across the surface. The only survivors would be those in airplanes, insofar as the airplanes withstand the turbulence and manage to land (and maybe people in parachutes or wing suits or other similar who can manage to glide through the turbulence until they can slow down enough to land safely).The next step after that would be for bodies of water to retain original velocity, in which case there would be even more massive tsunamis than those described in the book due to the oceans themselves flowing up onto the continents. I wonder how far the oceans would go. At furthest extent they wouldn't make it all the way across Russia and would flow around Tibet and other tall mountain ranges on the east sides of the continents. I suspect that more likely they wouldn't make it very far onto the America's due to being lined with mountains along the western edge, and wouldn't make it very far across the western parts of Africa and Europe.The next step after that would be that buildings and trees are not considered part of the earth, in which case they get uprooted with everything else. This gives Humanity a slightly better chance at survival as some of us might be able to "surf" on the flying buildings and possibly come to a rocky but survivable landing.Next after that would be to start including things that are on the earth but not "attached" to the main mass of the earth like rocks, dust, sand, topsoil. This would have a significant impact on the situation as on the one hand people would end up landing on more stuff that's been moving along with them, reducing the amount of skid-burn. On the other hand the amount of stuff flying across the surface would significantly increase the amount of turbulence and churn as things slowed down. I suspect the net result is more people surviving, though a lot of us would end up buried in a small layer of dirt/dust/whateverNext after that would be to start including mountains and hills. This ends up very similar to the previous one, perhaps with more people surviving due to more stuff to land on. This would also start to have an impact on the momentum of the earth itself, albeit pretty insignificant (it would make the Moon's job easier though).Next up is that the continents themselves maintain their original momentum, in which case the scenario totally changes as there wouldn't be the global windstorms, instead there would be global earthquakes. The first indication that something happened would be the sudden change in the magnetic field. The earthquakes would start miles below the surface and take a while to percolate, but once they hit it would flatten pretty much everything except for mountains and hills (which would still end up flatter). The seabed below the oceans would suddenly shift to the west, being stopped pretty quickly by friction. The day would be significantly lengthened probably to month-long or longer days. The water at the bottom of the ocean would heat up slightly from the friction, but otherwise wouldn't be affected much. However, the shift of the continents would expose some magma which would do more to heat up the sea in those areas which would result in significant changes in weather patterns and more severe storms. As the magma bubbled up, we might eventually witness the birth of some new mountain ranges, some of which may even break the surface.

Continuing any further would result in less and less noticeable earthquakes and changes in the length of the day, besides really stretching the definition of "earth" (the crust is definitely part of the earth. The continents are definitely part of the earth as well, but I figured I'd include that as it has some interesting consequences). Of course, these steps certainly have some gray areas around what each considers attached/part of the earth, like at what point do you consider a partially/wholly underground bunker part of the earth? What about man-made hills or landfills?

I'd we go with the idea of all the gasses keep moving while all solids and liquids stop presents some interesting details to look at. Consider the air inside people's lungs or inside buildings. In the latter case it might not make much difference except in underground structures and caves.